Five people have been detained in connection with the death of a university graduate who police say fell victim to scammers on a job-seeking website.

One of the five suspects is accused of playing a leading role in the scheme and the other four were detained for suspected unlawful detention, according to police in Tianjin's Jinghai district on Sunday.

All confessed that they lured Li Wenxing, a 23-year-old university graduate from Shandong province, into a pyramid scheme, the police said.

Early on Sunday morning, 2,000 law enforcement officers were sent out to catch scammers in Jinghai. They reported spotting 301 places in the district, and 63 people, involved in pyramid schemes.

The district government issued a statement on Sunday saying that any whistle-blower identifying such activity would be eligible for a reward of 20,000 yuan ($2,970).

Victims are lured to what they believe are regular companies, but are then instructed by the scammers－often under duress－to recruit friends and family or borrow money from them, according to the authorities. Mobile phones and identification documents are often confiscated, they say.

Scammers have been known to extort money and even to kidnap their targets.

According to police, a fraudulent employment advertisement was published on Zhipin, a recruitment website, which lured Li to Jinghai on May 20.

Investigators say Li paid the fee to the scammers for the recruitment and was forced to stay in the organization's dormitory. He was only allowed to move around the organization's premises, not outside.

Li's body was found on July 14 in a pond in Jinghai. The autopsy showed he drowned, but the circumstances that led to his death are still under investigation.

According to his family, Li asked his mother in his last call to her not to give money to anyone. Li's senior high school classmate Ding Xiangcheng said Li discussed the job offer with him before he left for Tianjin.

According to media reports, two of Li's high school classmates said Li borrowed 500 yuan from them before he was found dead.

The Commission for Political and Legal Affairs of the Communist Party of China Tianjin Committee launched a campaign against pyramid schemes recently.

Zhao Fei, head of the commission, said Jinghai is an area with rampant pyramid scheme activity and that the activities must be eliminated within 20 days.

Recruitment websites hosting unverified company information are common. The Cyberspace Administration of China launched a campaign last year targeting illegal activities related to recruitment websites, including fraud and offers of jobs from pyramid operations.